Method and conditioning agent for treating waste water and air pollutants

ABSTRACT

What is disclosed is a conditioning agent for the treatment of effluent and a process for preparing such a conditioning agent which includes a proportion of flocculating or precipitating agent containing polymers as well as a proportion of micro-organisms.

[0001] The invention relates to a process and a conditioning agent forthe treatment of effluent and atmospheric pollutants.

[0002] In the biological treatment of effluent or waste water,micro-organisms convert the organically usable ingredients of theeffluent to be purified into cell material or into gases such as, e.g.,CO₂, methane, hydrogen sulfide and others. Depending on the processmanagement, one differentiates between aerobic or anaerobic processes,wherein in communal effluent purification plants as a rule the aerobicprocesses are used which are better manageable. In such effluentpurification plants a mechanical purification is followed by biologicaldecomposition in an activated sludge tank wherein the carrier ofbiological purification, i.e., the sludge activated by micro-organisms,is received. Air is introduced into this activated sludge tank to thussupply the oxygen required for biological conversion. In this aerationof the effluent in the activated sludge or aeration tank there formslimy, macroscopically discernible flakes which settle as sedimentedsludge when aeration is completed.

[0003] In accordance with the publicationwww.uni-potsdamm.de/u/putz/oktober 1996/30.htm, organic or inorganicpolymers which support the growth of flakes are added to the effluent inorder to raise the efficiency of the biological conversion. The polymersare designed for the formation of flakes that are as compact and denseas possible and a surface with a low degree of unevenness, which lateragglomerate into larger conglomerates of flakes and thus are imperviousto the effect of shear forces owing to the flow of effluent.

[0004] The like flocculation aids are polymers having a different chargedensity, charge distribution, and molecular size depending on thepurpose to be achieved. They are used for the separation of solids fromsuspensions with organic or inorganic particles, which may bedistributed to a degree of colloidal consistency. Owing to the highadsorption potential, flocculation aide act as a link between the solidparticles and microflakes created by the use of flocculating agents,which build up into larger-size flakes (flocculation).

[0005] Besides the polymers acting as flocculation aids, theconditioning agent may moreover contain precipitation and flocculatingagents. In effluent purification, Al or Fe salts are frequently used asflocculating agents, which form precipitations having a very largesurface in particular ranges of pH. On these flakes heavy metals orother undesirable effluent components may be adsorbed. In effluentpurification, monomer salts e.g. of aluminum, calcium, iron andmagnesium, or polymer aluminum or iron compounds, respectively, are usedas precipitating agents.

[0006] Despite considerable progress in polymer chemistry, the presentconditioning agent may only be designed for an average composition ofthe effluent to be treated, wherein biological conversion may notsuffice requirements particularly in the event of biospherefluctuations, i.e., fluctuations of the proportion of organic matter inthe effluent to be treated.

[0007] In contrast, the invention is based on the objective offurnishing a conditioning agent and a process for the treatment ofeffluent and atmospheric pollutants, to provide effluent treatment whichis largely independent of fluctuations of the biosphere present in theeffluent.

[0008] This objective is attained by a conditioning agent in accordancewith claim 1, a process having the features of claim 10, and use of theconditioning agent in accordance with claim 15.

[0009] In accordance with the invention, the conditioning agent containsa predetermined proportion of micro-organisms, so that biologicalactivity is substantially determined by the microbiotic mixed culturescontained in the conditioning agent, and thus is largely independent ofthe composition of the micro-organisms contained in the effluent or inthe air. As will be described in more detail in the following, a stablebio-film forms on the surface of the polymers upon introduction of theconditioning agent containing the polymers and micro-organisms, whichbio-film is not destroyed even by high turbulence of the effluent. Thusan immobilization of the micro-organisms relative to the flake isachieved, resulting in largely ideal conditions for biologicalconversion.

[0010] It was surprisingly found that the conditioning agent may also beused for purifying air charged with pollutants.

[0011] In a particularly preferred embodiment the conditioning agentincludes a microbiotic mixed culture containing a proportion ofphotosynthetically active micro-organisms and a proportion of luminousbacteria in a biological solution.

[0012] As was mentioned at the outset, biopolymers and other organic orinorganic polymers are used as flocculation aids. Most recently interestis focusing on so-called conjugated polymers which emit light whenbinding a particular substance. Conjugated polymers consist ofsemiconductor materials and have hitherto predominantly been used forphysico-technical purposes, e.g. for solar cells or flat screens. Theluminescence of these semiconducting polymers may be used to completelyor partially replace the luminous bacteria of the microbiotic mixedculture.

[0013] Handling and storage of the conditioning agent is particularlysimple if the micro-organisms are deep-frozen or freeze-dried forstorage, wherein the process conditions upon cooling down have to beselected in such a way as to prevent damage to the micro-organisms.

[0014] With regard to the composition of the microbiotic mixed culture,for the sake of simplicity reference is made to the same applicant'searlier patent application DE 100 62 812, the contents of which areherewith fully included into the disclosure of the instant patentapplication.

[0015] Further advantageous developments of the invention are subjectmatters of the further subclaims.

[0016] Preferred embodiments of the invention shall in the following beexplained in more detail by referring to schematic drawings, wherein;

[0017]FIG. 1 is a block diagram of a process of the biological treatmentof effluent, and

[0018]FIG. 2 is a schematic representation of flake formation inaccordance with the invention.

[0019] In the following, a process for the biological treatment ofeffluent (communal, industrial effluent) is described by referring toFIG. 1, wherein a conditioning agent containing a proportion offlocculating and/or precipitating agents as well as precipitation aids,e.g. organic or inorganic and also conjugated polymers, is admixed tothe effluent in order to enhance flake growth. Such flocculating andprecipitating agents are substances bringing about an agglomeration ofthe suspended matter in the effluent and enabling more rapid separationof the solid phase from the liquid phase as a result of the obtainedsize increase of the particles. In addition to the polymers thisconditioning agent may contain further constituents like, e.g., metalsand other constituents that enhance flake formation. In accordance withthe invention the conditioning agent contains microbiotic mixed culturesin a defined composition, whereby substantially the metabolic reactionsin the flake are determined.

[0020] In accordance with the enclosed process diagram, a preferredembodiment of the microbiotic mixed culture (microbiologicalcomposition) contains a proportion of photosynthetically activemicro-organisms 1, a proportion of luminous bacteria or light-emittingmicro-organisms having similar activity 2, which are solubilized in abroad-band biological solution 4. As was mentioned at the outset, a partof the light-emitting micro-organisms may be replaced with conjugatedpolymers which emit light when particular biomolecules are present inthe microbiological composition.

[0021] The interaction between the photosynthetically activemicro-organisms and the luminous bacteria or the conjugated polymers hasthe result of the photosynthetically active micro-organisms beingstimulated to photosynthesis by the emitted light. The micro-organismsengage in photosynthesis with hydrogen sulfide and water as an educt andrelease sulfur or oxygen, respectively. Moreover they may bind nitrogenas well as phosphate and decompose organic as well as inorganic matter.

[0022] Preferably in the inventive microbiological compositionphotosynthetically active micro-organisms are used, which facultativelyare phototropic. Phototropic facultatively means that themicro-organisms can grow both under anaerobic conditions in light andunder aerobic conditions in the dark.

[0023] Among the photosynthesis bacteria there are gram-negative aerobicrod-shaped and circular bacteria and gram-positive circular bacteria.These may include endospores or be present without spores. Among themthere are for instance also gram-positive actinomycetes and relatedbacteria.

[0024] In this context it is also possible to name nitrogen-fixingorganisms. Among these there are, e.g., algae, such as Anabena Nostoc insymbiosis with Azola. Moreover it is possible to name actinomycetes,e.g. Frankia in symbiosis with alder and bacteria, such as Rhizobium insymbiosis with leguminosae.

[0025] Moreover it is also possible to use aerobic algae, azotobacter,methane-oxidizing bacteria and sulfur bacteria. Among these there arealso green sulfur bacteria and brown-green photosynthesis bacteria. Hereone may also name non-purple sulfur bacteria and purple sulfur bacteria.

[0026] It is preferred if, in the inventive microbiological composition,prochlorophytes, cyanobacteria, green sulfur bacteria, purple bacteria,chloroflexus-type forms and heliobacterium and heliobacillus-type formsare contained as facultatively phototropic micro-organisms. The abovenamed facultatively phototropic micro-organisms may also be present asmixtures of two or more of them. In a quite particular embodiment, allsix of the above named micro-organisms are present as a mixture.

[0027] The light which powers photosynthesis originates from theluminous bacteria contained in the microbiological composition of thepresent invention as the second essential component. These luminousbacteria possess luminosity, i.e., they are capable of emitting photons.This is a system that operates enzymatically. As an example, one mayhere name the luciferin/luciferase system.

[0028] In one preferred embodiment, Photobacterium phosphoreum, Vibriofischeri, Vibrio harveyi, Pseudomonas lucifera or Beneckea are containedin the inventive mixture as luminous bacteria. It is also possible toselect a mixture of at least two of these.

[0029] In order to optimize the inventive microbiological composition,additional constituents may be contained in it. Preferably suchsecondary constituents are plant extracts, enzymes, trace elements,polysaccharides, algin derivatives, other micro-organisms as mentionedabove. The secondary constituents may be present in the inventivemicrobiological composition by themselves or in combination. The plantextracts may, e.g., contain ribwort.

[0030] As a nutrient solution for the inventive microbiologicalcomposition, one will generally use a solution which contributes to theconstituents contained therein, in particular the micro-organisms, beingcapable to readily exist in it. Here it is of particular importance thatthe interaction of photosynthesis bacteria and luminous bacteriaachieves its full measure. It has been found that a biological nutrientsolution with molasses, in particular raw sugar or sugarbeet molasses,is suited as a main ingredient.

[0031] The photosynthetically active micro-organisms and the luminousbacteria normally are present in the inventive microbiologicalcomposition in a ratio of 1:10 to 1:500. A preferred ratio is 1:100.

[0032] The above described components are homogenized, so that as afirst intermediate product of the inventive process a microbioticculture 6 is present, the proportions of which are adjusted as afunction of the effluent to be treated.

[0033] In a subsequent process step B, the mixture is deep-frozen andoptionally freeze-dried in vacuum, so that the solvent, in the presentcase for example water constituents, are evaporated in the frozencondition (sublimation drying). Such a dehydration is a widely usedprocess for gentle drying and preservation of sensitive goods. Thedrying parameters are adjusted so as to preclude damage to themicro-organisms. It was found in preliminary trials that a cooling rateof more than 30° C. per minute, preferably about 40° C. per minute ormore rapid is optimal in order to prevent damage to the micro-organisms.

[0034] By this drying step the extra-cellular polymer substances (EPS)surrounding the cells of the micro-organisms are dehydrated, so that theslimy EPS layer is thickened and forms a protective layer which protectsthe micro-organisms during the freezing step.

[0035] The obtained, dehydrated product 9 is then mixed with aflocculating or precipitating agent containing the polymers in a mixingstage 12, and this mixture having a predetermined concentration is addedto an activated-sludge tank 14 containing effluent to be treated. Priorto mixing with the flocculating or precipitating agent 10, thedrying/freezing material is built up at reduced pressure, wherein areduced pressure of 0.01 millibar was found to be advantageous in firstpreliminary tests.

[0036] Oxygen is injected into the activated sludge tank, with theobjective to be achieved in terms of process technology being todistribute the oxygen as homogeneously as possible and keep the formingflakes suspended, so that a large and homogeneously distributed masstransfer surface and sufficient oxygen for biological conversion will bemade available.

[0037] The polymers introduced into the effluent form long chains havinga positive surface charge, on which the solid suspended mattercontaining the organic matter and generally having a negative surfacecharge deposit: this results in the formation of a germination cell, thegrowth of which i.a. depends on the type of flocculating agents, theactivity of the micro-organisms, and the composition of the effluent.

[0038] The inventive conditioning agent acts as a flocculating agent,thereby making it possible to withdraw substances dissolved in aneffluent or in a gas or substances distributed as a mist throughinclusion flocculation. The basic mechanism of this inclusionflocculation is represented in FIG. 2. The filament-shaped cationicpolyelectrolytes are for instance formed by proton-releasing Archaea andadded charge carriers, while the anionic polyelectrolytes are madeavailable by ion-releasing bacteria as well as the negative chargeenvironment in the effluent or in the charged air. In particular theproton-releasing micro-organisms that are present in the mixture depositon the sediments present in the effluent. These colloidal particles arethen, as shown in FIG. 2, enclosed between the cationic and anionicpolyelectrolytes and agglomerated into macroscopic flakes. The formingflake thus serves as a carrier for the micro-organisms which deposit inand on the flakes and colloidal particles. Nutrients are fixed whichprovide the micro-organisms in and on the flake for its growth. Inparticular applications it may be advantageous if the polymers and/ormicro-organisms are added continuously.

[0039] In the embodiment described by reference to FIG. 1, theconditioning agent was used for the treatment of effluent.

[0040] Another area of application of the inventive conditioning agentsis the purification of air charged with particulate pollutants or othergaseous matter. This set of problems shall be explained by way of aconcrete example.

[0041] For the laying of slabs of cork in the industrial range, as lateas into the 1960's customarily tar adhesives fabricated on the basis ofcoal-tar pitch or bitumen were employed. For laying the slabs of cork,these hot-melt adhesives were poured directly onto the slabs of cork andthen pressed to the walls, ceilings, and on the ground. In laying woodenflooring in the business and industrial areas, as well, adhesivescontaining tar or bitumen have been employed up to the present day.

[0042] These tar adhesives are not being produced any more in Germanysince the middle of the 1970's and have to be imported for thesepurposes. Cessation of the production of tar adhesives was enactedvoluntarily in Germany because in the meantime technically mature,innocuous surrogate products have. become available.

[0043] When structures incorporating materials bonded with tar adhesivesare demolished or altered, a considerable risk to the health of thepersons involved in demolition may exist, for the tar adhesives containextremely high concentrations of polycyclic aromatic hydrocarbons (PAK).For purposes of safe labor, suitable precautions have to be met in orderto preclude health hazards through dust emission and immediate skincontact. In other words, only specialized companies may be employed,while work procedures as low in dust as possible in conjunction witheffective evacuation of dust must be selected. In order to minimize therelease of dust upon breaking out the contaminated structuralcomponents, sufficient atomization of humidity (wetting) has to beprovided. Surprisingly it was found that the PAK concentration in theair may be reduced substantially with conventional solutions byadmixture of the inventive conditioning agent to the wetting agent(water), so that the health hazard during rebuilding of the likecontaminated structures may be reduced at comparatively small expense.By the cationic polyelectrolytes contained in the inventive conditioningagent the released PAK particles are again combined into a kind offlakes and bound to the original substance.

[0044] As was already mentioned above, it is possible to also usemicrobial biopolymers instead of synthetic polymers in the inventiveconditioning agent. Here it is possible, for example, to obtain aconsiderable increase of effectivity by the addition of chitin, which isthe most commonly occurring natural biopolymer besides cellulose.Chitosan is obtained enzymatically by microbial, biochemicaldecomposition of crustacean chitin. Chitosan has a positive ionic chargeand can therefore bind the negatively charged constituents in theeffluent or in the process air. The biopolymers usable for theconditioning agent may consist of a mixture and may be manufactured fromwaste products of sugar-producing industries. The biopolymer is readilywater-soluble with very high reactivity.

[0045] The micro-organisms contained in the inventive conditioning agentare chosen such that upon formation of a flake, a slimy extra-cellularpolymer substance (EPS) is produced, in which a number of bacteria cellsare embedded. As a result of this formation of slime, particularly atthe surface of the flake, a kind of protective screen against toxicsubstances (such as heavy metals) is formed, which prevents thesesubstances from penetrating inside the cell. The EPS may also act as asupporting structure for filiform kinds of bacteria. It is one moreeffect of the EPS that it acts as a diffusion barrier preventingdiffusion of substances required in the conversion, such as exo-enzymes,to the outside. Moreover bacteria living in symbiosis with other kindsuse the EPS as a means of being able to remain in spatial proximity ofthese bacteria.

[0046] The composition of the conditioning agent is chosen such that theforming flakes are surrounded by a complete EPS layer, so that thedecomposing and restructuring reactions may be performed. with anextremely high effectivity. The organic substances of the suppliedeffluent or of the charged process air to be purified are adsorbed bythe flake and oxidized or built into new cell substance, wherein a partof the flake itself is consumed.

[0047] The photosynthesis described at the outset takes place within theflake, so that the latter acts as a macroscopic “photo-bioreactor”.

[0048] In preliminary trials good results could be achieved with amixture comprised of ten volume parts of solubilized micro-organisms forone volume part of polymer. Here the microbiological solution maycontain about two percent (vol.) of micro-organisms.

[0049] It is another advantage of the inventive conditioning agent thatthe long polymer chains are cracked by the micro-organisms, so thatfurther processing of the resulting activated sludge is facilitated. Inexisting facilities, the long-chain polymers frequently constitute aconsiderable problem in terms of process technology as regards continuedprocessing of the sludges. Thanks to the improved biological conversion,resulting activated sludge may be decomposed substantially more rapidlythan in hitherto known processes in the digestion facility.

[0050] What is disclosed is a conditioning agent for the treatment ofeffluent and process air, a process for preparing such a conditioningagent, and use of the conditioning agent which includes a proportion offlocculating or precipitating agent containing polymers (biopolymers,conjugated polymers, other organic or inorganic polymers) as well as aproportion of micro-organisms.

1. A conditioning agent for the treatment of effluent or charged air,including a proportion of a polymer supporting flake formation orprecipitation, characterized by a proportion comprised of a microbioticmixed culture.
 2. The conditioning agent as claimed in claim 2, whereinsaid mixed culture contains photosynthetically active micro-organismsand luminous bacteria in a biological solution.
 3. The conditioningagent as claimed in claim 2 or 3, wherein said mixed culture isdeep-frozen or freeze-dried prior to being mixed with said polymers. 4.The conditioning agent as claimed in claim 2 or 3, whereinprochlorophytes, cyanobacteria, green sulfur bacteria, purple bacteria,chloroflexus-type forms and heliobacterium and heliobacillus-type formsas well as mixtures of two or more of these are contained in saidmixture as facultatively phototropic micro-organisms.
 5. Theconditioning agent as claimed in any one of claims 2 to 4, whereinphotobacterium phosphoreum, Vibrio fischeri, Vibrio harveyi, Pseudomonaslucifera or Beneckea or mixtures of at least two of these are containedin said mixture as luminous bacteria.
 6. The conditioning agent asclaimed in at least one of claims 2 to 5, wherein it furthermorecontains plant extracts, enzymes, trace elements, polysaccharides, alginderivatives, other micro-organisms as secondary constituents, either bythemselves or in combination.
 7. The conditioning agent as claimed inany one of the preceding claims 2 to 6, having one volume part offlocculation aids for ten volume parts of mixed culture (micro-organismplus solution).
 8. The conditioning agent as claimed in any one of thepreceding claims, wherein said polymer is a conjugated polymer.
 9. Theconditioning agent as claimed in any one of claims 1 to 7, wherein saidconditioning agent contains biopolymers.
 10. A process for preparing aconditioning agent for the biological purification of effluent,including the steps: preparing a polymer or a mixture of polymers actingas a flocculating or precipitating agent; preparing a microbiotic mixedculture with micro-organisms in a biological solution; mixing said mixedculture with said mixture of polymers.
 11. The process as claimed inclaim 10, wherein said mixed culture is deep-frozen or freeze-dried. 12.The process as claimed in claim 10 or 11, wherein said mixed culture iscooled down to a temperature below −50°C.
 13. The process as claimed inany one of claims 10 to 12, wherein said mixed culture is thawed priorto mixing with said mixture of polymers, preferably under reducedpressure.
 14. The process as claimed in any one of claims 8 to 13,wherein upon introduction of said conditioning agent into effluent, saidmixed culture forms a bio-film on the surface of a flake forming on saidpolymers.
 15. Use of a conditioning agent as claimed in any one ofclaims 1 to 9, for binding particulate atmospheric pollutants.
 16. Theuse as claimed in claim 1, wherein said conditioning agent is added to awetting agent which is sprayed in the form of a mist.